The production of mixed cultures containing strains of Lactococcus lactis, Leuconostoc cremoris and Lactobacillus rhamnosus , on commercial starter media

Abstract

Mixed starters containing Lactococcus lactis, Leuconostoc cremoris and Lactobacillus rhamnosus strains were produced on commercial starter media (MB Complete, Thermolac, Marlac), as well as on milk. With the exception of Marlac, the starters were cultured under pH control. The effect of media and incubation temperature (22 or 32 degrees C) on population ratios, on specific acidifying activities (SAA) of the cultures as well as on their ability to produce aroma compounds in milk was studied. The starters had higher contents in lactobacilli when they were produced at 32 degrees C, whereas a tendency to obtain higher Leuconostoc populations was observed at 22 degrees C. With respect to the lactococci, there was a significant interaction between temperature and growth medium for both strains. Thus, Le. cremoris T2 reached higher populations at 32 degrees C if grown in MB complete and Thermolac, whereas in Marlac and skim milk, viable counts were higher at 22 degrees C. The lactococci represented 50% of the total population of the culture at the beginning of the incubation, but they composed between 80% and 99% of the total population following fermentation. The best medium for growth of Leuconostoc was milk, but populations of only 10(8) cfu/ml were reached. The lactobacilli did not grow well in MB Complete, and their development was best in the low-phosphate Marlac medium. The cultures grown on Marlac had the highest SAA values, whereas those grown on MB complete had the lowest. Overall, more ethanol and diacetyl were detected in the fermented milks when the starters used to inoculate them were produced at 22 degrees C.

Leuconostoc, characteristics, use in dairy technology and prospects in functional foods

“…A balanced growth of species occurs during incubation between 21 C and 25 C. At temperature above 25 C, the ratio is skewed toward the metabolically more active Lc. lactis, which grows at a faster rate at higher temperature (between 25 C and 32 C) relative to the Leuconostoc (Vedamuthu, 1994; Liu et al, 1997;Baron, Roy, & Vuillemard, 2000;Barrette et al, 2000).…”

Fresh-cheesemilk formulation fermented by a combination of freeze-dried citrate-positive cultures and exopolysaccharide-producing lactobacilli with liquid lactococcal starters

“…Diacetyl and acetaldehyde were analysed by gas chromatography as described by Barrette et al (2000).…”

“…cremoris strains, and mixed cultures containing aroma-producing strains are traditionally grown in milk without pH control (Harvey, 1965;Hugenholtz, 1986;Thu- nell, 1988). In addition, it was shown that Leuconostoc cremoris and Lactobacillus rhamnosus cultures do not compete well with the lactococci in commercial starter media used under external pH control (Barrette, Champagne, Roy, & Rodrigue, 2000). Therefore, preparing mixed cultures under pH control is not an easy task.…”

“…Lb. rhamnosus RW-9595M is an EPS-producing strain (Dupont, Roy, & Lapointe, 2000;Macedo, Lacroix, Gardner, & Champagne, 2002), which can grow at 15°C and was used in a prior study with mesophilic cultures (Barrette et al, 2000). It was thus selected for this study in the aim of improving the texture of the fresh cheeses, and potentially providing probiotic features.…”

Functional implications of the microbial community structure of undefined mesophilic starter cultures

“…At temperatures above 25°C, L. lactis grows substantially faster than Leuconostoc sp. [40], whereas at temperatures between 21°C and 25°C a more balanced growth of both genera is observed [39]. During the initial phase of cheese manufacturing, Le.…”